Bumping gaia.json for 2 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/adc015c126d8
Author: Casey Yee <cyee@mozilla.com>
Desc: Merge pull request #14141 from Joshua-S/bug-941622

[Bug 941622] - [Contacts] Update background and sub header colour
r=arnau

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https://hg.mozilla.org/integration/gaia-central/rev/4e009a8649d7
Author: Joshua Smith <joshua-smith@verizon.net>
Desc: Bug 941622 - [Contacts] Update background and sub header colour